Generation of polyurethane foam

ABSTRACT

An improvement in the generation of foam from a mixture of foam-forming material in a structure having a preferred configuration. Conveying means are used to convey the structure along a horizontal path. A plurality of foam gun heads are mounted in spaced relationship to each other over and transverse to said horizontal path. Each foam gun head includes a foam dispensing outlet and valve means for controlling the discharges of the foam-forming materials therefrom. First, sensing means are provided upstream of the foam dispensing outlets for sensing the passage of the structure thereby. A plurality of second sensing means are positioned upstream of the foam dispensing outlets in spaced relationship to each other in a direction transverse to the horizontal path, each one of the second sensing means being associated with one foam gun head for sensing the presence of the structure in a vertical direction. The valve means in a foam gun head is opened in response to the first sensing means sensing the structure and its associated second sensing means also sensing the structure. The valve means of a given foam gun head is closed in response to its associated second sensing means detecting the absence of structure.

This is a division of application Ser. No. 762,555, filed Jan. 25, 1977.

BACKGROUND OF THE INVENTION

This invention relates to improvements in the generation of polyurethanefoam. More particularly, the present invention relates to improvementsin the generation of polyurethane foam wherein a multi-foam gun headdispensing system is used to generate foam in a structure having apreformed configuration.

The present invention has particular application to the generation anddispensing of polyurethane foam into relatively large surface areas. Forexample, polyurethane foam may be used to provide insulation betweenbuilding panels. Such panels may be used in the construction ofrelatively large buildings and comprise a shell of concrete or otherbuilding material having a core of polyurethane foam therein forinsulating purposes. Such core may be considered a foam "slab". The foamslab may be generated by dispensing the foam-forming materials directlyinto one-half of the building panel or into a mold.

In dispensing polyurethane foam into such large surface areas, onepreviously known method has been to utilize a single foam dispensing gunhead and allow the foam to flow to cover the area. However, the foambegins to rise into its full free-rise volume immediately upon beingdispensed from the foam gun head. Thus, there has been problems withobtaining foam slabs having a uniform density throughout. In addition,the overall average density of such foam slab is higher which affectsits overall economics.

In considering an automatic system for dispensing foam generatingmaterial, problems arise due to the fact that the width and/or length oftwo different foam slab configurations may vary by design. In addition,in some instances it is desirable to have openings in the foam slab toprovide windows or doors in the ultimate panel. This adds to the problemof providing an efficient automated system.

SUMMARY OF THE INVENTION

The present invention has as its object, the overcoming of the problemsdiscussed above.

In accordance with the present invention, there is provided a noveltechnique for dispensing polyurethane foam into panels or molds wherebythe foam is evenly distributed over the surface area.

In addition, according to the present invention, the foam dispensingtechnique of the present invention takes into consideration variationsin the width and/or length between two different molds or panels.

Further, the present invention also takes into consideration that agiven panel or mold may have an opening therein wherein no foam-formingmaterial is desired.

These and other objects and advantages of the present invention may beachieved, according to the preferred embodiment of the presentinvention, through the provision of an apparatus having conveying meansfor conveying the structure into which the foam-forming materials are tobe dispensed along a horizontal path. A plurality of foam gun heads aremounted in spaced relationship to each other and transversely to saidhorizontal path. Each foam gun head may include a foam dispensing outletand valve means for controlling the discharge of the foam formingmaterial therefrom. First sensing means are provided upstream of thefoam dispensing outlets for sensing the passage of the structurethereby. A plurality of second sensing means are positioned upstream ofthe foam dispensing outlets in spaced relationship to one another in adirection transverse to said horizontal path, one of said second sensingmeans being associated with each foam gun head for sensing the presenceof said structure in a vertical direction. Means are provided foropening the valve means of each foam gun head in response to the firstsensing means sensing the structure and an associated second sensingmeans also sensing said structure, and for closing the valve means of agiven foam gun head in response to its associated second sensing meansdetecting the absence of structure.

In accordance with the preferred method of the present invention, thestructure into which the foam-forming materials are to be dispersed isconveyed along a horizontal path underneath a plurality of foam gunheads having outlets spaced transversely of said path. The presence ofthe structure is sensed at a point upstream of the foam gun head,outlets by a first sensing means. The presense of the structure issensed in a vertical direction at a point upstream of the foam gun headoutlets by a plurality of second sensing means which are spaced fromeach other in a direction transverse to said horizontal path, one ofsaid second sensing means to being associated with one of said foam gunheads. The valve means of a given foam gun head is opened in response tothe first sensing means sensing the presence of structure and itsassociated second sensing, sensing the presence of structure. The valvemeans of a given foam gun head is closed in response to its associatedsecond sensing means sensing the absence of structure.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the general arrangement of theapparatus of the present invention;

FIG. 2 is a schematic illustration showing the details of variousmaterial flow paths of the apparatus of FIG. 1;

FIG. 3 is a schematic illustration showing the details of the variousactuators of the apparatus of FIG. 1; and

FIG. 4 is a schematic illustration of an electrical circuit which may beused in the apparatus of FIG. 1.

DETAILED DESCRIPTION

Referring to the drawings, and in particular to FIG. 1, there is shownan apparatus used to practice the present invention. The apparatus,according to the present invention, generally includes a tower 2 fromwhich foam is dispensed into a structure such as a panel or mold 4passing therethrough The panel of mold 4 is transported by a continuousconveyor 8 to the tower 2 and removed therefrom by a second continuousconveyor 12.

The tower 2 includes an upper cabinet 14 which houses a plurality offoam dispensing gun heads 15 having nozzles 16 which extend in avertical direction from the underside of the cabinet 14. The foam gunheads 15 are spaced apart from each other in a direction transverse ofthe direction of movement of the panel or mold 4 as shown in FIG. 1. Anynumber of foam gun heads may be used depending upon the width of thewidest panel or mold to be used. Directly underneath the nozzles 16 ofthe foam gun heads 15 is a trough 18 which is moveable between lowerposition wherein its upper surface is substantially flush with a bottomcabinet 20 and a raised position wherein the nozzles 16 extendthereinto.

The tower 2 also includes a horizontally directed photocell 22 having alight source 24 which supplies a light beam 23 extending horizontally,across the path of travel of the mold of panel 4. Downstream of thehorizontally directed photocell 22, but slightly upstream of the nozzles16, are a series of vertically directed photocells 26, one associatedwith each of the foam gun heads 15 and positioned in the bottom cabinet20. The upper cabinet 14 is provided with a corresponding light source28 for each of the vertically directed photocells 26 which directs avertical light beam 27 from the bottom of the upper cabinet 14 to itscorresponding photocell 26 positioned in the lower cabinet 20.

Referring now to FIG. 2, the apparatus includes a first storage tank 30which houses a first reactant material and a second storage tank 32which houses a second reactant material. The storage tanks 30 and 32 maybe located remote from the tower 2. Each of the reactants containedwithin its respective storage tanks 30 or 32 is pumped through asuitable delivery line 34 or 36, respectively, to its respectivemanifold 38 or 40 located within the upper cabinet 14 for distributionto each of the foam gun heads 15.

The apparatus also includes a solvent storage tank 42 to provide asupply of solvent through a delivery line 44 to a manifold 46 locatedwithin the upper cabinet 14 for distribution to each of the foam gunheads 15 for the cleansing thereof. A supply of purge gas such ascompressed air may be supplied to the foam gun heads 15 from acompresser 48 through a suitable conduit 50 into a manifold 52 alsolocated within the upper cabinet 14 for purging each of the foam gunheads 15.

More in detail, the present invention in its preferred form is useful inthe generation and dispensing of two reactive ingredients commonly usedto produce polyurethane foam. In general, polyurethane foam may beproduced by the reaction of a polyol with an organic polyisocyanate inthe presence of a reaction catalyst and a foaming agent. Any knownfoam-forming formulation may be generated by, and dispensed from theapparatus of the present invention. The polyol reactant may be anymaterial having at least two active hydrogens as determined by theZerewitinoff method, such as described, for example, in U.S. Pat. No.3,167,528, issued Jan. 26, 1965 to Kaiser et al. Similarly, any organicisocyanate containing at least two NCO groups may be utilized inpreparing the foam. Illustrative polyisocyanates include toluenediisocyanates and the polymeric isocyanates such as disclosed in U.S.Pat. No. 2,683,730, issued July 13, 1954 to Seeger et al. The foamingagent may be any one of those known in the art to be useful for suchpurpose such as water, an organic foaming agent, or a mixture of atleast two foaming agents. Illustrative organic foaming agents aredisclosed in U.S. Pat. No. 3,072,582, issued Jan. 8, 1963 to Frost. Anycatalyst or mixture of catalysts known to be useful in makingpolyurethane foam may be employed such as disclosed for example, in U.S.Pat. No. 3,397,158 issued to Britain et al, on Aug. 13, 1968.

In utilizing the apparatus of the present invention, a first reactantmaterial comprising the organic polyisocyanate or a polyisocyanatepolyol pre-polymer may be stored in one of the reactant storage tanks,for example, the first storage tank 30. In the other reactant storagetank, the second storage tank 32, the polyol may be stored.Conveniently, a reaction catalyst may also be included in this tank. Thefoaming agent may be supplied from a third storage tank or, as ispreferred, the foaming agent may be included in at least one andpreferably both of the storage tanks 30 and 32.

A suitable solvent for the reactant materials is stored in the solventstorage tank 42. Such solvent may be methylene chloride,1,1,1-trichlorethane, or any other solvent suitable for the purpose.

The foam gun heads 15 are preferably of the type described in U.S. Pat.No, 3,409,044, issued to Sobek et al. on Nov. 5, 1968, the entiredisclosure of which is incorporated herein by reference. Each foam gunhead 15, as shown in that patent, includes two valved passagewaysleading to a mixing chamber which communicates with the outlet of thenozzle 16. If desired, the interior of each nozzle 16 may be providedwith a static mixer and form part of the mixing chamber. One suitablestatic mixer is described in U.S. Pat. No. 3,286,992, issued toArmeniades et al. on Nov. 22, 1966, the entire disclosure of which isincorporated herein by reference. A suitable foam gun head having astatic mixer is shown and described in U.S. patent application Ser. No.656,157, filed Feb. 9, 1976, in the name of J. F. Zwirlein, commonlyassigned the entire disclosure of which is incorporated herein byreference.

Each foam gun head 15 includes two valve actuators 54 and 56 to open andclose the valves in the valved passageways leading to the mixingchamber. The valve actuators 54 and 56 are operated simultaneously bymeans of a double acting air cylinder 58 (see FIG. 3) having a pistonand piston rod 60 therein with the piston rod 60 connected to connectinglinks 62 and 64.

The first reactant material is supplied, at a predetermined constantpressure maintained by any suitable means such as a pump 66 or aconstant pressure gas supply 67, from its storage tank 30 to itsmanifold 38. One pasaageway of each of the foam gun heads 15 isconnected to the first reactant manifold 38 by a suitable connectingline 68. The connecting line 68 may be provided with a manually actuatedon-off valve 70 which may be used for repair and maintenance purposes. Afilter element 72 may also be included in line 68 to remove any foreign,solid particles which may be present in the reactant material flowing tothe foam gun head 15. It is also preferred to interpose in line 68 aflow control unit 74 in order to regulate the flow of the reactantmaterial. Any suitable type of flow controller may be used such as thedevice described in U.S. Pat. No. 3,541,023 issued to Cole on Nov. 17,1970. A one-way check valve 76 may also be provided in line 68 adjacentto the entrance to the passageway in the foam gun head 15.

The second reactant material is supplied, at a constant pressuremaintained by any suitable means such as a pump 78 on a constantpressure gas supply 79, from its storage tank 32 through its deliveryline 36 to its manifold 40. The other passageway of each foam gun head15 is connected to the second reactant manifold 40 by a suitableconnecting line 80. In a like manner to the connecting line 68, theconnecting line 80 may include a manually actuated on-off valve 82, afilter element 84, a flow control unit 86, and a one-way check valve 88.The use of the flow control units 74 and 86 in each of the lines 68 and80 respectively, enables the reactant materials to be supplied to thefoam gun head 15 in a predetermined ratio. Flow control units of thetype detailed in FIGS. 3 and 4 of the above-mentioned Cole patentincorporate means to enable the adjustment of the flow therethrough toany desired constant rate. With such an arrangement, the relativeproportions of the reactants flowing to the foam gun head through lines68 and 80 can be varied depending upon their respective compositionsand/or viscosities.

The solvent is forced, at a constant pressure maintained by any suitablemeans such as a pump 90 or a constant pressure gas supply 91, from itsstorage tank 42 to its manifold 46 through its connecting line 44. Eachfoam gun head 15 has a central inlet communicating with the mixingchamber such as shown in the above-mentioned patent application Ser. No.656,157. This inlet is connected to the outlet of a connector 92 havingtwo inlets by a suitable connecting line 94. One inlet of each of theconnectors 92 is connected to the solvent manifold 46 through aconnecting line 96. Each connecting line 96 includes a manually operatedshut-off valve 98 for repair and maintenance purposes, and apneumatically operated ball valve 100 which is the on-off valve used tocontrol the flow of solvent to the foam gun head 15 during operation. Aone-way check valve 102 may also be provided in line 96 adjacent theconnector 92.

The supply of pressurized fluid is supplied to its manifold 52 throughits delivery line 50. The pressurized fluid may be compressed air or anyother gas suitable for purging the foam gun head. If the gas iscompressed air, the air may be supplied by a separate compressor 48 orany other available source of compreseed air.

The other outlet of each connector 92 associated with each foam gun head15 is connected to the purge gas manifold 52 by a suitable connectingline 104. Each connecting line 104 includes a manually operated shut-offvalve 106 for repair and maintenance purposes, and an electricallyoperated on-off solenoid valve 108 which is the on-off control valve forthe purge gas. A check valve 110 may be provided in line 104 adjacentthe connector 92.

Referring now to FIG. 3, the various valve operators are shownschematically. The valve 108 in each purge gas line 104 is a solenoidvalve and has its electrical connector 112 directly connected to theelectrical circuit of FIG. 4.

The ball valve 100 in each solvent connecting line 96 is pheumaticallyoperated by means of a double acting air cylinder 114. The air cylinder114 includes a piston and piston rod 116 mechanically connected to thevalve 100 so that when the piston rod 116 is moved to one position thevalve 100 is opened and when returned to its original position, thevalve 100 is closed. The air cylinder 114 is in turn controlled by atwo-way electrically operated solenoid valve 118 provided in the line120 supplying the operating fluid to the air cylinder 114. The solenoidvalve 118 is electrically connected to the electrical circuit of FIG. 4.

For the purpose of supply operating fluid to the various air cylindersof the apparatus, a manifold 122 may be provided in the upper cabinet towhich the various air cylinders may be connected. The manifold 122 maybe connected to any suitable supply of operating fluid such ascompressed air.

The solenoid valve 118 associated with air cylinder 114 serves to directthe operating fluid to one side of the piston or the other. When thesolenoid is not energized, the valve 118 is in one position so that theoperating fluid is directed through passage 124 to move the piston andpiston rod 116 into the position wherein the ball valve 100 is closed.When the solenoid is electrically actuated, the valve 120 closes offpassage 124 and directs air through passage 126 to the other side of thepiston to move the piston and piston rod 116 into a position wherein theball valve 100 is opened.

The valve actuators 54 and 56 used to actuate the valves in each of thefoam gun heads 15 to dispense the reactants into the mixing chamber andout of the nozzle 16 are operated by the double acting air cylinder 58.The piston rod 60 of the air cylinder 58 is connected to connectinglinks 62 and 64 which in turn are connected to the actuators 54 and 56,respectively. The arrangement is such that when the piston rod 60 ismoved downwardly from its position as shown in FIG. 3, the valveactuators 54 and 56 are rotated about an axis extending perpendicular tothe axis of the piston rod 60 and the valves in the passageways in thefoam gun head 15 open and permit the flow of the reactants from lines 68and 80 to enter the mixing chamber in the foam gun head 15 and bedispensed from the nozzle 16 thereof. When the piston rod 60 is returnedto its original position, the valves in the passageways in the foam gunhead are closed.

The operation of the air cylinder 58 is controlled by a two-wayelectrically operated solenoid valve 128 provided in the line 130supplying the operating fluid to the air cylinder 58. The line 130 isconnected to the operating fluid manifold 122. The solenoid valve 128serves to direct the operating fluid to one side of the piston or theother. When the solenoid is not energized, the valve 128 is in oneposition to direct the operating fluid through passage 132 to move thepiston and piston rod 60 into an upper position (as viewed in FIG. 3)and close the valves in the foam gun head 15. When the solenoid iselectrically actuated, the valve 128 closes off passage 132 and directsair through passage 134 to the other side of the piston and moves thepiston and piston rod 66 into a lower position (as viewed in FIG. 3) toopen the valves in the foam gun head 15. The solenoid valve 128 iselectrically connected to the electrical circuit shown in FIG. 4.

The trough 18 is mounted in the lower cabinet for movement between alower position substantially flush with the top of the bottom cabinet 20and a raised position wherein the nozzles 16 of each foam gun head 15extend thereinto. The trough 18 is moved by an air cylinder 136 having amoveable piston and piston rod 138 therein. The free end of the pistonrod 138 is connected to the trough 18 so that the trough 18 will risewhen the piston rod 138 is moved upwardly (as viewed in FIG. 3) and willlower when the piston rod 138 moves downwardly.

The operation of the air cylinder 136 is controlled by an electricallyoperated two-way solenoid valve 140 provided in the line 142 supplyingthe operating fluid to the air cylinder 138. The line 142 may beconnected to manifold 122 or any other source of pressurized operatingfluid. The solenoid valve 140 serves to direct the operating fluid toone side of the piston or the other. The solenoid valve 140 is connectedto the electrical circuit of FIG. 4. When the solenoid of the valve 140is not energized, the valve 140 directs the operating fluid throughpassage 144 to move the piston and piston rod 138 into its lowerposition, lowering the trough 18 into its lower position. When thesolenoid of valve 140 is energized, the valve 140 closes off passageway144 and directs the operating fluid through passageway 146 to move thepiston and piston rod 138 upwardly and thereby raise the trough 18 intoits raised position. Although only one air cylinder 136 is shown in FIG.3 for raising the lowering the trough 18, additional air cylinders,operated as explained above, may be utilized, if desired.

FIG. 4 is a schematic illustration of the electrical connection of thevarious actuators of the apparatus of the present invention. Theelectrical circuit includes a master on-off switch 148 which is of themanual type. The switch 148 is used to energize and de-energize theelectrical circuit when the switch is turned on or off respectively. Thehorizontally directed photocell 22 is in series with the switch 148 andeach of the vertically directed photocells 26. All of the photocells 22and 26 are of the type which, when actuated by a light beam from theirassociated light source, open the electrical circuit and when the lightbeam is broken, close the electrical circuit.

Each of the photocells 26 are electrically connected to a time delayrelay 151 which when actuated, closes after a predetermined period oftime to supply current from conductor 153 to its associated solenoid ofthe solenoid valve 128 which is used to control the air flow to thedouble acting air cylinder used to operate the valve actuators 54 and 56of the foam gun head 15.

The photocell 22 is also electrically connected in series by anelectrical connector 150 to a relay circuit 152 which has three outputs154, 156 and 158. Output 154 is connected through a time delay relay 160to the solenoid of each solenoid valve 108 which is used to control theflow of compressed air to the foam gun heads 15. Output 156 is connectedthrough a time delay relay 162 to the solenoid of each of the solenoidvalves 118 which is used to control the flow of the pneumatic fluid tothe air cylinder 114 used to actuate the ball valve 100 to control theflow of the solvent to the foam gun heads 15. The output 158 isconnected through a time delay relay 164 to the solenoid of the solenoidvalve 140 used to control the flow of the pneumatic fluid to the doubleacting air cylinder 136 used for raising and lowering the trough.

The relay circuit 152 is connected to a suitable power source 165through the on-off switch 148 by electrical connector 166. The relaycircuit 152 serves to connect the power source 165 through conductor 166to the outputs 154, 156 and 158 when actuated by the photocell 22through conductor 150. A "ready" switch 167 is also provided which, whenactuated, resets all relays 150, 160, 162 and 164 to an active positionbefore a new sequence can start.

A conveyor drive circuit is also shown in FIG. 4 for driving theconveyor 8 and 12. A variable speed electric motor 168 may be used todrive the conveyor 8 and 12. For this purpose, the output shaft of themotor 168 is connected to a drive roller 169 associated with eachconveyor 8 and 12 by a suitable mechanical drive train arrangement suchas a sproket and gear arrangement 170. A motor control circuit 172 isprovided to control the motor 168 along with manually-actuated on-offswitch 174 to start the conveyor in motion. A manually adjustable speedcontrol 176 is connected to the motor control circuit 172 so that theconveyor speed may be varied by manual adjustment.

A relay 178 may be provided in the circuit leading to the solenoids 128and 108, 118, 140 such as shown in FIG. 3 which is normally open, butwhich is closed when the conveyor drive is operating. This preventsopening of the valves of the foam gun heads 15, the opening of solventvalve 100, the air purge valve 108 and the raising of the trough 18,unless the conveyors 8 and 12 are in motion.

Relay circuit 152 is normally open when photocell 22 is contacted by thelight beam 23 from source 24 and current is flowing through conductor150. When the light beam 23 to photocell 22 is broken and current flowsthrough conductor 150, relay circuit 152 is still open but is set foractuation. After light beam 23 is restored and the circuit throughconductor 150 reopened, whereby no current flows through conductor 150the relay circuit 152 will close, permitting current to flow fromconductor 166, through the circuit 152 to the outputs 154, 156 and 158and the time delay relays 160, 162 and 164 respectively. The time delayrelays 160, 162 and 164 are of the type which are normally open, butclose after a predetermined period of time after actuation to permitcurrent to pass through the relay circuit 152 to the solenoids of valves108, 118 and 140 for a predetermined period of time whereupon the relays160, 162 and 164 open again.

In operation, with the master on-off switch 2 on so that the circuit isclosed, and with the "ready" switch 167 having been actuated to resetthe relays 128, 160, 162 and 164 the photocells 22 are actuated by thebeam of light from source 24 so that no current passes from power source165 to time delays 151. When light beam 23 is broken by the passage ofthe mold or panel 4 to be filled, the circuit through the photocell 22is closed, providing current to photocells 26 and the relay circuit 151.The photocells 26, receiving a beam of light, are normally open untilthe beam of light is interrupted. When the beam of light to a givenphotocell 26 is broken, the circuit is closed and current will pass toits associated relay 151, which after a predetermined time delay, willclose. Upon closing of a relay 151, a current will pass from conductor153 through the relay 151 to its associated solenoid valve 128 causingactuation of the valve 128 and operation of its associated foam gunhead. The valve 128 will remain actuated as long as the beam to itsrespective photocell 26 is broken. When the beam to a given photocell 26is again restored, no current passes from the photocell 26 to the relay151, and the relay will open after a predetermined time period, causingdeactuation if valve 128 and closing of the valves in its associatedfoam gun head.

Upon breaking of the light beam to photocell 22 by the passage of themold or panel thereby, the circuit is also closed to the relay circuit152 through conductor 150. This readies the relay circuit 152 for lateractuation. When the panel or mold 4 completely passes by the photocell22 and the photocell 22 again senses a light beam from its light source,which results in closing of the valves in the form gun heads 15, thecircuit through conductor 150 is opened. Upon opening of this circuit,the relay circuit 152 closes to permit the passage of current fromconductor 166 through the circuit 152 to outputs 154, 156 and 158,actuating the time delay relays 160, 162 and 164. The time delay relay164 is set to close after a slight time delay, whereupon the solenoid ofsolenoid valve 140 is actuated causing the solenoid valve 140 to admitpneumatic fluid to the air cylinder 136 to raise the trough 18 to itsupper position.

The time delay relay 162 is set to close after the passage of a suitabletime period to allow the trough 18 to raise. After passage of such timeperiod, the time delay relay 162 closes, activating the solenoid of eachsolenoid valve 118 to open valve 100 in the solvent lines 96 to permitsolvent to flow to each gun heads 15 for cleaning purposes. After apredetermined time period, the time delay relay 162 closes, the solenoidof the solvent valve 118 is de-energized, and the valve 100 in thesolvent line is closed.

The time delay relay 160 is set to close at about the same time as thetime delay relay 162 re-opens. There may be a slight overlapping in timebetween the time the air purge is commenced and the solvent flow is shutoff. Upon closing of the time delay relay 160, the circuit to thesolenoid of solenoid valve 108 is closed and the solenoid valve 108 inthe air purge line is opened for a predetermined short period of time.After such period of time, the time delay relay 160 opens whereupon theair purge solenoid valve 108 is closed.

The time delay relay 164, controlling the acutation of the trough 18, isset to remain closed, thereby maintaining the trough in its raisedposition, until the air purge valve 108 has been closed by opening ofthe time delay relay 160. After this predetermined period of time, thetime delay relay 164 will close, whereupon the solenoid valve 140 willswitch and admit fluid to the air cylinder 136 to cause the trough 18 toreturn to its lower position.

To begin a new sequence of operation, the ready switch 167 must beactivated to set the various time delay relays. Thereafter, the passageof a panel or mold 4 past the photocells 22 and 26 will cause theoperation of the foam gun heads 15 and, after the foam gun heads 15 havebeen deactivated, the sequence of raising the trough, activating anddeactivating the solvent flow, activating and deactivating the air purgeand lowering of the trough 18 as explained above.

As mentioned above, the present invention may be used for making foamslabs useful as an insulating core in structural panels. Varioustechniques may be used in fabricating such insulated panels. In oneinstance, one half of the building panel may be used as a mold intowhich the foam is dispensed. Immediately after the panel is filled withfoam, and before the free-rise volume of the foam has been obtained, theother half of the panel may be placed on top of the bottom panel whichcontains the foam, and the two panels held together under pressure untilthe foam cures, providing a completed building panel. Alternatively, thefoam may be dispensed into the bottom panel and the foam allowed to riseto its full free-rise volume after which the top panel may be fittedover the bottom and connected thereto, compressing the foamtherebetween, and providing a final assembly. Yet another alternative isto utilize a mold to preform the foam slab. In such a case, the foam isdispensed into the mold, and either allowed to free rise, or immediatelycontained by a top mold, and the "slab" resulting therefrom after curingcan then be used as the core in a later operation when the actualbuilding panels are assembled.

Referring again to FIG. 1, the structure 4 into which the foam-formingmixture is dispensed, whether it be one-half of a structural panel or amold, includes a bottom 180 and side walls 182. If it is necessary toprovide an opening in the resulting foam slab for a window or door, thebottom of the structure is cut away and side walls are providedsurrounding the opening as indicated at 184 in FIG. 1.

The operation of the apparatus in dispensing the foam-formingingredients into a structure 4 such as shown in FIG. 1 is as follows.The on-off switch 148 of the apparatus is turned on and the "ready"switch 167 is activated to set the various relays in the electricalcircuit. The motor speed control 176 may then be set to obtain theproper conveyor speed. It is to be noted that the rate of flow of thereactant materials from each nozzle 16 of a foam gun head 15 ismaintained constant. Therefore, the thickness of the foam is dependentupon the rate of speed at which the structure 4 passes under the nozzles16. The slower the structure moves, the thicker the foam will be in thestructure and visa versa. As the conveyors 8 and 12 control the speed ofmovement of the structure along its horizontal path under the nozzles16, the thickness of the foam may be controlled by adjusting the speedof the conveyors.

After the conveyor switch 174 has been turned on, the structure 4 willmove on the conveyor 8 toward the tower 2. The light beam from lightsource 26 will extend across the path of travel of the structure 4 tothe photocell 22. The light beams from all light sources 28 will extendvertically toward their associated photocells 26.

When the front end of the structure 4 passes by photocell 22 and breaksthe light beam, the electrical circuit is put into a "go" condition asexplained above. When the bottom 180 of the structure breaks one of thelight beams to one of the vertically extending photocells 26, itsassociated foam-gun head 15 discharges the foam-forming mixture from itsnozzle 16 into the structure 4. It is to be noted that only those foamgun heads whose associated light beams are broken are activated. Thus,if a relatively narrow structure 4 is being used which does not extendall the way across the horizontal path, one or more outer foam gun headswhose light beam is not broken by the bottom of the structure 4, willnot be activated. Thus, the apparatus can automatically adjust the widthof the dispension of the foam-forming materials to take into account thewidth of the mold of panel into which the materials are being dispensed.

When an opening in the structure, such as opening 184 in FIG. 1, passesover one or more photocells 26, the light beam to such photocell isrestored which serves to stop the flow of material from its associatedfoam gun head. Thus, no foam will be dispensed into the opening where itis not needed. After the opening 184 has passed by the photocell 26, thebottom of the structure will again break the light beam and thatparticular foam gun head will again be actuated.

Each foam gun head 15 will continue to dispense foam as long as thehorizontal light beam to photocell 22 is broken and the vertical lightbeam to its associated photocell 26 is broken. When the horizontal lightbeam to photocell 22 is restored, after passage of the structurethereby, the foam gun heads 15 will be turned off after a predeterminedtime period sufficient to permit the end of the structure to reach thenozzles. Thus, by virtue of the arraggement of this invention, anylength of structure may be used with the present apparatus.

After a predetermined time interval passes after the end of thestructure 4 passes the photocell 22 and the light beam is restoredthereto, the trough 18 is raised into its upper position surrounding thenozzles 16. Thereafter, the solvent valve 100 to each foam gun head 15is opened for a predetermined time period and all the foam gun heads 15are flushed with solvent to cleanse them to remove any residualfoam-forming materials. The raising of the trough 18 to its upperposition prevents excessive splattering of solvent and residualfoam-forming materials which could result in injury to person orproperty, or contamination. The trough 18 may be provided with a drain186 which may be connected to a suitable container for collecting thesolvent.

After the solvent flush has terminated, the air purge valves 108 to eachfoam gun head 15 are opened to provide a gas blast through each foam gun15 to complete the cleansing. In some instances, it may be desirable tostart the air purge slightly before the solvent flush has finished.

After the air purge, the trough 18 is returned to its lower position.The apparatus is then ready to receive another structure 4 after the"ready" switch 167 is activated, whereupon, the above sequences arerepeated. However, no adjustments will have to be made to the apparatusif the new structure 4 is of a different width or length than thepreceeding structure, or if an opening 184 is provided in differentlocations. The apparatus of the present invention automatically controlsthe operation of the foam gun heads 15 in a manner that only those foamgun heads 15 which are needed are utilized to dispense the foam-formingingredients.

While reference has been made above to a preferred embodiment of thepresent invention, it will be apparent to those skilled in the art thatvarious modifications and alterations my be made thereto withoutdeparting from spirit of the present invention. Therefore it is intendedthat the scope of this invention be ascertained by reference to thefollowing claims.

I claim:
 1. An apparatus for generating foam from a mixture offoam-forming materials in a structure having a preformed configuration,said apparatus comprising:conveyor means for conveying such a structurealong a horizontal path; a plurality of foam gun heads mounted in spacedrelationship to each other over and transversely to said horizontalpath, each foam gun head including a foam dispensing outlet and valvemeans operatively associated with said outlet for controlling thedischarge of the foam-forming materials therefrom; first sensing meansupstream of said foam dispensing outlets for sensing the passage of sucha structure thereby; a plurality of second sensing means positionedupstream of said foam dispensing outlets in spaced relationship to eachother in a direction transverse to said horizontal path, each one ofsaid second sensing means being associated with one foam gun head forsensing in a vertical direction the presence of such a structure; andmeans for opening said valve means of each foam gun head in response tothe first sensing means sensing such a structue and its associatedsecond sensing means sensing such a structure, and for closing the valvemeans of a given foam gun head in response to its associated secondsensing means detecting the absence of structure.
 2. The apparatus ofclaim 1 wherein said first sensing means includes a horizontallydirected photocell and means spaced therefrom for directing a firstlight beam thereto horizontally and transversely to said horizontalpath, said light beam adapted to be broken when such a structure passesthrough the first beam.
 3. The apparatus of claim 1 wherein each saidsecond sensing means includes a vertically directed photocell and meansspaced therefrom for directing a second light beam thereto in a verticaldirection, said beam adapted to be broken when such a bottom portion ofthe structure passes through the second beam.
 4. The apparatus of claim1 wherein each said foam gun head has an inlet for the admission of asolvent, each said inlet being connected to a supply of solvent, saidapparatus further including solvent control means for controlling theflow of solvent to each said foam gun head, said solvent control meansincluding means responsive to said first sensing means sensing theabsence of structure after such a structure has passed thereby foradmitting solvent to said foam gun head for a predetermined period oftime.
 5. The apparatus of claim 4 wherein said solvent control meansadmits said solvent to said foam gun head after a predetermined periodof time has passed from the time said first sensing means has sensed theabsence of structure after such a structure has passed thereby.
 6. Theapparatus of claim 4 wherein each said foam gun head has an inlet forthe admission of a purging gas, each said inlet being connected to asupply of purging gas, said apparatus further including purge gascontrol means for controlling the flow of purge gas to each said foamgun head, said purging gas control means including means responsive tosaid first sensing means sensing the absence of structure after such astructure has passed thereby for admitting solvent to said foam gun headfor a predetermined period of time beginning at least after said solventhas begun to be admitted to said foam gun head and ending after thepredetermined time period for said solvent .
 7. The apparatus of claim 6further including a trough normally disposed below said horizontal pathand in alignment with said foam gun heads, means for moving said troughbetween a normally disposed position and a raised position, and troughcontrol means for raising and lowering said trough, said trough controlmeans including means responsive to said first sensing means sensing theabsence of stucture after such a structure has passed thereby to raisesaid trough before said solvent flush and lower said trough after saidpredetermined period of time for admittance of said solvent.
 8. Theapparatus of claim 7 wherein said trough control means includes an aircylinder and solenoid valve for actuating said air cylinder.
 9. Theapparatus of claim 6 wherein said purge gas control means includes asolenoid valve.
 10. The apparatus of claim 4 wherein said solventcontrol means includes a pneumatically operated valve and a solenoidvalve for controlling the pneumatic operation of said pneumaticallyoperated valve.
 11. The apparatus of claim 1 wherein said means foropening and closing said valve means of said foam gun head includes anair cylinder and a solenoid valve for actuating said air cylinder.